sort_in_topological_order(): avoid setting a commit flag

We used to set the TOPOSORT flag of commits during the topological
sorting, but we can just as well use the member "indegree" for it:
indegree is now incremented by 1 in the cases where the commit used
to have the TOPOSORT flag.

This is the same behavior as before, since indegree could not be
non-zero when TOPOSORT was unset.

Incidentally, this fixes the bug in show-branch where the 8th column
was not shown: show-branch sorts the commits in topological order,
assuming that all the commit flags are available for show-branch's
private matters.

But this was not true: TOPOSORT was identical to the flag corresponding
to the 8th ref.  So the flags for the 8th column were unset by the
topological sorting.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.h

@@ -12,8 +12,7 @@
 #define CHILD_SHOWN	(1u<<6)
 #define ADDED		(1u<<7)	/* Parents already parsed and added? */
 #define SYMMETRIC_LEFT	(1u<<8)
-#define TOPOSORT	(1u<<9)	/* In the active toposort list.. */
-#define ALL_REV_FLAGS	((1u<<10)-1)
+#define ALL_REV_FLAGS	((1u<<9)-1)
 
 struct rev_info;
 struct log_info;